Therapeutic vascular occlusions (embolizations) are induced by the introduction of various substances (embolic material, such as embolic particles) into a patient's circulatory system for the purpose of occluding vessels, either to arrest or to prevent hemorrhaging or to defunctionalize a structure or an organ. Typically, the components of an embolic composition-embolic particles in hydrating material (such as saline) and contrast agent (used for tracking the path of the embolic particles inside the body) are stored separately and mixed together at the time of injection into the body by the physician.